Polymer Mixtures Research Articles

CRYSTALLIZATION OF MODIFIED COMPOSITES BASED ON ALUMINUM HYDROXIDE AND POLYETHYLENE MIXTURE

The article presents the results of a dilatometric study of the crystallization of modified with structure-forming agent composites based on aluminum hydroxide and a mixture of high and low density polyethylenes. The influence of aluminum hydroxide concentration on the regularity of the change in the dependence of the specific volume, as well as the free specific volume on temperature, has been established. The crystallization onset temperature and the approximate values of the glass transition temperature of composite materials are determined. The studies were carried out in the process of stepwise cooling of the samples at a load of 5.3 kg on an IIRT-1 device converted into a dilatometer. The concentration of aluminum hydroxide varied within 1–30 wt.%. A mixture of high and low density polyethylene was taken in a 50/50 ratio. Titanium dioxide was used as a structure-forming agent in an amount of 1.0 wt.%. It has been established that with an increase in the concentration of aluminum hydroxide, the crystallization onset temperature of modified composites based on a mixture of polyethylenes remains unchanged and is equal to 1050C. It is shown that with an increase in the content of aluminum hydroxide in the polymer mixture, a regular increase in the density of the composites is observed

Development of controlled-release matrix tablets of anti-diabetic agent using natural and synthetic polymers

The aim of this study was to develop and produce natural polymer-based controlled-release matrix tablets of metformin hydrochloride. The formulations were manufactured from a mixture of natural and synthetic polymers, including gum copal, gum damar, gum olibanum, xanthum gum, and hydroxypropyl methylcellulose (HPMC) K15M. The granules were characterized by Fourier transform infrared spectroscopy (FTIR). The kinetics of drug release from the formulations was determined by zero-order kinetic analysis. The formulas were found to be in the following ranges: 4.20.054 to 5.10.58 ​kg/cm2, 844.86.84 to 852.64.13 ​mg, 0.230.002 to 0.670.048 percent, and 99.450.15 to 101.930.16 percent, respectively. For all formulations, it was found that Carr's index, Hausner's ratio, bulk density, tapped density, and angle of repose were less than 15% and 1.18, respectively, indicating that the generated tablets had acceptable flow properties. Formulations F3, F4, and F5, which contained varying amounts of gum copal, showed respective drug release rates of 91.21 percent, 85.69 percent, or 99.87 percent after 12 ​h. For formulations F11, F12, and F13, which included varying quantities of olibazine gum, after 10, 10, and 9.5 ​h, it generated 100% drug release after 10, 10.5, and 10 ​h. Formulation F5 which included gum copal, and the HPMC showed sufficient release to exert the necessary therapeutic effect in under 12 ​h, whereas the other formulations showed anomalous or non-Fickian diffusion. This study suggests that matrix tablets for continuous controlled release can be made.

Modification of electrodes with polymer nanocomposites: Application to the simultaneous determination of Zn(II), Cd(II), and Cu(II) in water samples

Currently, there is a need for fast and sensitive analytical methods for monitoring metals in water due to the progressive increase in the presence of metal ions in the environment. These metals reach the environment mainly from industrial activity and heavy metals are non-biodegradable. The present work evaluates different polymeric nanocomposites to carry out the simultaneous electrochemical determination of Cu, Cd, and Zn in water samples. Screen-printed carbon electrodes (SPCE) were modified with the nanocomposites, which were obtained by a mixture of graphene, graphite oxide, and polymers, such as polyethyleneimide, gelatin, and chitosan. These polymers have amino groups in their matrix, giving the nanocomposite the ability to retain divalent cations. However, the availability of these groups plays a fundamental role in the retention of these metals. The modified SPCEs were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The electrode that presented the best performance was selected to determine the concentration of metal ions in water samples by square-wave anodic stripping voltammetry. The obtained detection limits were 0.23 μg L−1, 0.53 μg L−1, and 1.52 μg L−1 for Zn(II), Cd(II), and Cu(II), respectively, with a lineal range of 0.1–50 μg L−1. The obtained results made it possible to conclude that the method developed using the SPCE modified with the polymeric nanocomposite presented adequate LODs, reasonable sensitivity, selectivity, and reproducibility. Besides, this platform is an excellent tool for developing devices to simultaneously determine heavy metals in environmental samples.

3D Porous Scaffold-Based High-Throughput Platform for Cancer Drug Screening.

Natural polymer-based porous scaffolds have been investigated to serve as three-dimensional (3D) tumor models for drug screening owing to their structural properties with better resemblance to human tumor microenvironments than two-dimensional (2D) cell cultures. In this study, a 3D chitosan-hyaluronic acid (CHA) composite porous scaffold with tunable pore size (60, 120 and 180 µm) was produced by freeze-drying and fabricated into a 96-array platform for high-throughput screening (HTS) of cancer therapeutics. We adopted a self-designed rapid dispensing system to handle the highly viscous CHA polymer mixture and achieved a fast and cost-effective large-batch production of the 3D HTS platform. In addition, the adjustable pore size of the scaffold can accommodate cancer cells from different sources to better mimic the in vivo malignancy. Three human glioblastoma multiforme (GBM) cell lines were tested on the scaffolds to reveal the influence of pore size on cell growth kinetics, tumor spheroid morphology, gene expression and dose-dependent drug response. Our results showed that the three GBM cell lines showed different trends of drug resistance on CHA scaffolds of varying pore size, which reflects the intertumoral heterogeneity across patients in clinical practice. Our results also demonstrated the necessity to have a tunable 3D porous scaffold for adapting the heterogeneous tumor to generate the optimal HTS outcomes. It was also found that CHA scaffolds can produce a uniform cellular response (CV < 0.15) and a wide drug screening window (Z' > 0.5) on par with commercialized tissue culture plates, and therefore, can serve as a qualified HTS platform. This CHA scaffold-based HTS platform may provide an improved alternative to traditional 2D-cell-based HTS for future cancer study and novel drug discovery.

Stability Studies, Biodegradation Tests, and Mechanical Properties of Sodium Alginate and Gellan Gum Beads Containing Surfactant.

The excessive presence of single-use plastics is rapidly degrading our natural environment on a global scale due to their inherent resistance to decomposition. Wet wipes used for personal or household purposes contribute significantly to the accumulation of plastic waste. One potential solution to address this problem involves developing eco-friendly materials that possess the ability to degrade naturally while retaining their washing capabilities. For this purpose, the beads from sodium alginate, gellan gum, and a mixture of these natural polymers containing surfactant were produced using the ionotropic gelation method. Stability studies of the beads by observing their appearance and diameter were performed after incubation in solutions of different pH values. The images showed that macroparticles were reduced in size in an acidic medium and swelled in solution of pH-neutral phosphate-buffered saline. Moreover, all the beads first swelled and then degraded in alkaline conditions. The beads based on gellan gum and combining both polymers were the least sensitive to pH changes. The compression tests revealed that the stiffness of all macroparticles decreased with the increasing pH of the solutions in which they were immersed. The studied beads were more rigid in an acidic solution than in alkaline conditions. The biodegradation of macroparticles was assessed using a respirometric method in soil and seawater. It is important to note that the macroparticles degraded more rapidly in soil than in seawater.

78‐3: Piezoresistive Area Sensor with Polymer and CNTs Mixture on Oxide TFT Backplane

We demonstrate a highly sensitive, lateral pressure sensor using carbon nanotubes (CNTs) embedded in styrene‐ethylene‐butadiene‐styrene (SEBS) layer on 48 x 48 AM backplane for pressure mapping. The sensor exhibits highly sensitive, piezoresistive performances with current ratio of ~10 6 with a broad detection range of 330 Pa to 28 kPa, and response and recovery times of less than 10 ms and 20 ms, respectively.

Encapsulation of Carbon Nanotubes by Styrene and Butyl Acrylate Particles via Suspension Polymerization for Polymerized Toner Applications.

Electrophotographic printing and copying processes primarily use toner, which is a mixture of colorant, polymer, and additives. Toner can be made using traditional mechanical milling techniques or more contemporary chemical polymerization techniques. Suspension polymerization provides spherical particles with less stabilizer adsorption, homogeneous monomers, higher purity, and easier control of the reaction temperature. In contrast to these advantages, however, the particle size resulting from suspension polymerization is too large for toner. To overcome this disadvantage, devices such as high-speed stirrers and homogenizers can be used to reduce the size of the droplets. This research investigated the use of carbon nanotubes (CNTs) instead of carbon black as the pigment in toner development. We succeeded in achieving a good dispersion of four different types of CNT, specifically modified with NH2 and Boron or unmodified with long or short chains in water rather than chloroform, using sodium n-dodecyl sulfate as a stabilizer. We then performed polymerization of the monomers styrene and butyl acrylate in the presence of the different CNT types and found that the best monomer conversion and largest particles (in the micron range) occurred with CNTs modified with boron. The insertion of a charge control agent into the polymerized particles was achieved. Monomer conversion of over 90% was realized with all concentrations of MEP-51, whereas conversion was under 70% with all concentrations of MEC-88. Furthermore, analysis with dynamic light scattering and scanning electron microscopy (SEM) indicated that all polymerized particles were in the micron size range, suggesting that our newly developed toner particles were less harmful and environmentally friendly products than those typically and commercially available. The SEM micrographs clearly showed good dispersion and attachment of the CNTs on the polymerized particles (no CNT aggregation was found), which has never been published before.

Chain-Increment Approach to the Mutual Miscibility of Polymers with All-Atom Molecular Simulation

The mutual miscibility of polymers was addressed with all-atom molecular dynamics (MD) simulation and the energy-representation theory of solvation. The chain-increment method was extended to polymer mixtures, and the mixing free energy was related to the incremental free energy for the constituent polymer species that is the free-energy change of turning on the interaction of a monomer in the tagged polymer chain with the surrounding molecules. The free energy was then computed for the mixing of polyethylene (PE) and poly(vinylidene difluoride) (PVDF) and of poly(vinyl alcohol) (PVA) and polyvinylpyrrolidone (PVP). It was seen that the incremental free energy is insensitive to the location of the monomer in the inner part of the polymer chain and depends on the mixing ratio of the polymer system in parallel with the average interaction energy of the incremented monomer with the surrounding polymers. The intermolecular interactions of each polymer species were further analyzed at atomic resolution. The PVDF–PVDF interaction was found to become less favorable (more positive) upon addition of PE in the mixture of PE and PVDF, making them immiscible with each other. PVP favors PVA more than PVP, on the other hand, leading to the miscibility of PVA and PVP. The connection of our formulation of the mixing free energy with the Flory–Huggins expression is also described.

Electroactive molecularly imprinted polymer nanoparticles for selective glyphosate determination

Redox-active molecularly imprinted polymer nanoparticles selective for glyphosate, MIP-Gly NPs, were devised, synthesized, and subsequently integrated onto platinum screen-printed electrodes (Pt-SPEs) to fabricate a chemosensor for selective determination of glyphosate (Gly) without the need for redox probe in the test solution. That was because, ferrocenylmethyl methacrylate was added to the polymerization mixtures during the NPs synthesis so that the resulting MIP-Gly NPs contained covalently immobilized ferrocenyl moieties as the reporting redox ingredient, conferring these NPs with electroactive properties. MIP-Gly NPs of four different compositions were evaluated. The herein described approach represents a simple and effective way to endow MIP NPs with electrochemical reporting capabilities with neither the need to functionalize them post-synthesis nor to use electrochemical mediators present in the tested solution during the analyte determinations. MIP-Gly NPs synthesized using allylamine and squaramide-based monomers appeared most selective to Gly. The Pt-SPEs modified with MIP-Gly NPs were characterized with differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Changes in the DPV peak originating from the oxidation of the ferrocenyl moieties in these MIP-Gly NPs served as the analytical signal. The DPV limit of detection and the linear dynamic concentration range for Gly were 3.7 pM and 25 pM–500 pM, respectively. Moreover, the selectivity of the fabricated chemosensors was sufficiently high to determine Gly successfully in spiked river water samples.

SYNTHESIS AND PROPERTIES OF THE METHYL ESTERS OF 3,5-DI-METHYLCYCLOALKYL-4-HYDROXYPHENYLPROPIONIC ACID

A study was carried out and a method was developed for the synthesis of sterically hindered phenols by cycloalkylation of methyl ester of 4-hydroxyphenylpropionic acid with 1-methylcyclopentene, 1- and 3-methylcyclohexene in the presence of a KU-23 catalyst (modification 10/60 (GOST 20298)) with a pore radius of 250-600 Å. The optimal conditions for cycloalkylation of methyl ester of 4-hydroxyphenylpropionic acid with methylcyclenes in the presence of a KU-23 catalyst (temperature 100-110 ºС, reaction time 5-6 h, molar ratio of ether to cyclene 1:2, amount of catalyst 10% per taken ester) were determined. At these conditions, the highest values of yields and selectivity of the target product are achieved. The yields of the target products were 69.8-72.5% of the theory for the taken ester and the selectivity was 89.6-94.3% for the target product. The chemical structures of the synthesized methyl esters of 3,5-di-cycloalkyl-4-hydroxyphenylpropionic acid were confirmed by spectral methods of analysis, the purity and fractional composition – by chromatographic methods of analysis. For the compounds the physicochemical parameters, molecular weight were determined and elemental analysis was carried out. For the processes of catalytic cycloalkylation of methyl ester of 4-hydroxyphenylpropionic acid with methylcyclenes the material balance was calculated and compiled. The synthesized methyl esters of 3,5-dicycloalkyl-4-hydroxyphenylpropionic acid were tested as stabilizers for the polyurethane polymer. Esters were added during the synthesis of a polyurethane polymer. Then the membrane were prepared from a mixture of polymer and ester. These membranes were subjected to light and heat aging at a temperature of 150 °C for 6 h, UV irradiation for 40 h. Based on the tests carried out, it was found that methyl ester of 3,5-di-(1-methylcyclohexyl)-4-hydroxyphenylpropionic acid can be recommended for use as a heat stabilizer for polyurethane polymer and face coverings for artificial leather based on it. For citation: Naghiyeva M.V., Rasulov Ch.K. Synthesis and properties of the methyl esters of 3,5-dimethylcycloalkyl-4-hydroxyphenylpropionic acid. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 85-93. DOI: 10.6060/ivkkt.20236606.6777.

Preparation and Application of Polymeric Molecularly Imprinted Adsorbents in Accordance with the Principles of Green Chemistry

Molecularly imprinting technology is a suitable tool for the development of selective materials for the isolation and separation of substances, and targeted use. The aim of this paper was to compile an overview of current trends in the preparation of MIP (Molecularly Imprinted Polymers). We focused on the implementation of ecologically acceptable solutions in the procedures for the fabrication and application of MIP, mainly for the purposes of chemical analyses. Theoretical approaches and simulations for the selection of optimal components of the polymerization mixture, the application of ultrasonic and microwave light in MIP synthesis, as well as microextraction procedures for the preparation of complex samples for analysis are successfully applied in analytical methods based on MIP adsorbents. While the use of low transition temperature mixtures (deep eutectic solvents, ionic liquids) and biomass components as a replacement or modification of porogens, functional and cross-linking monomers or other components of the polymerization mixture can help to transform the polymerization processes into more environment-friendly ones, it still requires an investigation of the synthesis mechanisms and their influence on the properties of the prepared MIPs.

Synthesis and rheological properties of water soluble ionic copolymers as modifier fluids at high temperature and saline media

AbstractPolymer flooding depicts an interesting strategy to improve the enhanced oil recovery (EOR). This work aims with the synthesis of ionic thermo‐responsive copolymers able to be used as rheological modifiers for EOR under harsh conditions (250,000 ppm of NaCl at 150°C). Copolymers composed of different molar ratio of acrylamide, N‐isopropylacrylamide and 2‐acrylamide‐2‐methyl‐1‐propanesulfonic acid were prepared in aqueous media via free radical polymerization at 50°C using 4,4′‐azobis(‐4″‐cyanopentanoic) acid (ACPA) as initiator. Nuclear magnetic resonance analyses demonstrated the structure and molar composition of synthesized copolymers. Rheological measurements performed at different concentration from 1 to 8 wt% demonstrated an increase in the viscosity from 2000 to 600,000 mPa.s. Aqueous mixtures of polymer at 5 wt% and NaCl at different concentration (5, 10, 15, 20, and 25 wt%) was analyzed. Copolymer ([PAM]/[PNIPAM] = 50/50) displayed a phase separation at 15 wt% of NaCl. Solutions of polymer at 5 and 25 wt% of NaCl were heated at 150°C for 72 h. Results revealed both thermal stability and saline tolerance of copolymers [PAM]/[PNIPAM]/[PAMPS‐Na] = 25/25/50, 35/35/30, and 50/0/50 under harsh conditions with the absence of phase separation of the brine polymer solutions.

Xanthan gum and Tara gum galactomannans have a synergistic effect on gelation properties

Rheology is essential for assessing the applicability of bio-based and renewable polymers because it provides crucial information about their mechanical properties, flow behavior, and processing characteristics. So, gels formed by carbohydrate polymer mixtures have specific rheological properties that can be used in the food industry to improve processes, develop new products, or replace ingredients. The aim of the research was to characterize the interactions and synergy of the aqueous mixture of Xanthan gum (XG) and Tara gum (TG). Commercial TG was previously purified, and aqueous mixtures were prepared using varying concentrations of XG and TG. Rheological properties were determined using a rotational rheometer. An equation was proposed to quantify the degree of solid behavior of the formed gel as a function of its mechanical properties. Pure TG or XG in aqueous solution exhibited pseudoplastic behavior. At a 0.4% w/w concentration, the XG solution displayed a “weak gel” behavior. The concentrations of XG and TG in the aqueous mixture of the gums had a significant effect on the gel strength, presenting a region of maximum value, limited between the concentrations of 0.4–0.5% TG and 0.2–0.3% XG. The greatest strength of the gel was obtained at intermediate concentrations of gum; however, the value of the strain limit displayed a linear increase with TG concentration, confirming the synergistic effect on the solid-like behavior and strength of the gel.

Optical characteristics and bacterial-resistance ability of PVA/ZnO nanocomposites

Poly(vinyl alcohol) (PVA) thin films with different amounts of zinc oxide (ZnO) nanoparticles (NPs) (0.001, 0.002, 0.003, 0.004 and 0.005 ​g) were prepared using the casting method. The structural characteristics of the PVA polymer, ZnONPs and the mixture of polymer and ZnO NPs with a particle size of 80 ​nm have been studied using X-ray diffraction, Scanning Electron Microscopy and Fourier Transform Infrared spectroscopy. The optical characteristics of PVA/ZnO nanocomposites were studied in the wavelength range of 200–700 ​nm. According to experimental research, adding more ZnONPs to nanocomposites improves the PVA polymer's absorbance, absorption coefficient, extinction coefficient, refractive index and real and imaginary dielectric constants. As the amount of ZnONPs increases, the transmittance and energy gap of the PVA polymer decrease. Research on the antibacterial activity of these nanocomposites was conducted using Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella quasipneumoniae subsp. Similipneumoniae as pathogen microorganisms. According to the findings, the antibacterial activity of NPs is greatly influenced by their chemical make-up and form. Moreover, increasing the amount of ZnO in the composites causes an increase in antibacterial activity.

Dynamic crosslinking compatibilizes immiscible mixed plastics.

The global plastics problem is a trifecta, greatly affecting environment, energy and climate1-4. Many innovative closed/open-loop plastics recycling or upcycling strategies have been proposed or developed5-16, addressing various aspects of the issues underpinning the achievement of a circular economy17-19. In this context, reusing mixed-plastics waste presents a particular challenge with no current effective closed-loop solution20. This is because such mixed plastics, especially polar/apolar polymer mixtures, are typically incompatible and phase separate, leading to materials with substantially inferior properties. To address this key barrier, here we introduce a new compatibilization strategy that installs dynamic crosslinkers into several classes of binary, ternary and postconsumer immiscible polymer mixtures in situ. Our combined experimental and modelling studies show that specifically designed classes of dynamic crosslinker can reactivate mixed-plastics chains, represented here by apolar polyolefins and polar polyesters, by compatibilizing them via dynamic formation of graft multiblock copolymers. The resulting in-situ-generated dynamic thermosets exhibit intrinsic reprocessability and enhanced tensile strength and creep resistance relative to virgin plastics. This approach avoids the need for de/reconstruction and thus potentially provides an alternative, facile route towards the recovery of the endowed energy and materials value of individual plastics.

ВЛИЯНИЕ ПРИМЕНЕНИЯ ПОЛИМЕРНЫХ СТРУКТУРООБРАЗОВАТЕЛЕЙ НА ФИТОТОКСИЧНОСТЬ АГРОЧЕРНОЗЕМА

The use of polymer structure–forming agents in agriculture is a promising method of reducing soil erosion. An important condition for application is the assessment of the phytotoxicity of the polymer composition. The effect of polymer compositions VPRG® (VPRG) and VPK-402® (VPK) on the growth of the Trifolium rubens plant was studied in the laboratory on agrochernozem. The degree of influence was assessed by the change in the dry mass of the upper part of the plants relative to the control. It was found that the use of VPRG in doses of 106, 212 and 424 kg/ha per 10 m3 of water, and VPK in doses of 280 and 560 l/ha per 10 m3 of water did not have a toxic effect on the germination and growth of the Trifolium rubens plant. The dry weight of the upper part of the plants grown using these doses of polymers exceeded the control values by 1.14–1.47 times. The use of ВПК at a dose of 1120 g/ha per 10 m3 of water, as well as mixtures of polymers of VPRG and VPK in doses of (106 kg/ha of VPRG)/(280 l/ha of VPK) per 10 m3 of water and (424 kg/ha of VPRG)/(140 l/ha of VPK) per 10 m3 water had a negative effect on the growth of the red clover plant: the weight of the dry mass of the upper part of the plant decreased by 1.1–2.0 times relative to the control.

Impact of Ag Nanoparticles on the Spectral and Optical Properties of Electrospun Nanofibrous Poly(vinyl alcohol)–Poly(acrylamide)

Nanofibers based on the polymer mixture that was associated with poly(vinyl alcohol) (PVA) and poly(acrylamide) (PAAm) (50/50 wt.%) doped with different ratios of silver nanoparticles (Ag NPs) were successfully synthesized using electrospun method, which was performed at room temperature (RT) and high voltage (12 kV). The products were studied using techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR), X-ray diffraction (XRD) and ultraviolet–visible absorption spectroscopy. SEM results show uniform structures and a smooth surface without particles visible on the surface of the nanofibers. Also, SEM images show that the average diameter of polymer blend nanofibers is 157.40 nm and decreases with the increasing concentration of Ag NPs. The small capacity of the carbonyl group to operate as a powerful electron donor for interacting with [Formula: see text] cation is shown by the fact that the FTIR signal strength decreases with increasing dopant concentration, indicating an increase in the basicity of the major functional groups. The X-ray diffraction pattern results confirm the amorphous nature (nano-crystalline) of the PVA–PAAm. The XRD results show that the crystallite size increases with the increase of the concentration of Ag and the peaks of weak intensity at a concentration of 6% agree with Ag in the cubic structure. Indirect allowed and forbidden transition optical energy gap values decreased with increasing Ag NPs content. The effect of doping on the other parameters (absorption coefficients, refraction index and extinction coefficient) of different blend behavior was investigated in detail which qualifies them for solar cell applications.

Study on PET Recovery from Polymeric Mixtures, Using the Floatation Technique, and Valorization of the Collected Particles by Dyeing Them

The aim of this study is to separate PET flakes by applying floatation technique, initially from binary polymer blends and later from the mixture of five common polymers such as polypropylene, polyethylene, poly(vinyl chloride), polstyrene and poly(ethylene terephthalate). A connection line between polymer and fiber is presumed in this study, because the dyeing of recovered polyester with three disperse dyes followed. The separation of plastics was performed in a Plexiglas air floatation column. The Lutensol® TO 8 surfactant of non-ionic origin was used to selectively wet the plastics. The parameters studied were pH values, surfactant concentration and treatment time. The dyeing of the recovered PET was performed with Serilene Blue RL, Serisol Crimson ECF and Serisol Yellow ECF dyes at 90 °C, 110 °C, 130 °C and pH = 4.6. The results obtained showed a good separation of polyester from both the binary mixtures and the mixture of five polymers with a recovery rate of up to 95 ± 2%. The influence of pH and concentration of surfactant is significantly demonstrated, while the effect of the treatment time is considered negligible. Finally, recovered polyester showed very good dyeing properties with all three disperse dyes, since the color exhaustion rate reached approximately 95% for the temperature of 130 °C, which is the usual dyeing temperature of polyester.

The Relationship between Gelation Behavior and the Amount of Polymer Dose per Silica Surface Area of "Shake-Gels" Consisting of Silica Nanoparticles and Poly(Ethylene Oxide).

The understanding and control of the rheological behaviors of colloids and polymer mixtures is an important issue for scientific interests and industrial applications. Aqueous mixed suspensions of silica nanoparticles and poly(ethylene oxide) (PEO) under certain conditions are interesting systems called "shake-gels", whose states vary reversibly between sol-like and gel-like under repeated shaking and being left to stand. Previous studies have indicated that the amount of PEO dose per silica surface area (Cp) is a crucial parameter for the formation of shake-gels and the relaxation time from gel-like to sol-like states. However, the relationship between the gelation dynamics and the Cp values has not been fully investigated. To determine how the gelation dynamics are affected by the Cp, we measured the time taken for silica and PEO mixtures to gelate from the sol-like to gel-like states as a function of the Cp under different shear rates and flow types. Our results show that the gelation time decreased with increasing shear rates and depended on the Cp values. Moreover, the minimum gelation time was found around a certain Cp (=0.03 mg/m2) for the first time. The finding suggests that there is an optimum Cp value at which the bridging of silica nanoparticles using PEO is significant, and thus, the shake-gels and stable gel-like states are most likely to form.

Straightforward Creation of Possibly Prebiotic Complex Mixtures of Thiol-Rich Peptides.

At the origin of life, extremely diverse mixtures of oligomers and polymers could be obtained from relatively simple molecular bricks. Here, we present an example of the polymerization of two amidonitriles derived from cysteine, Cys-Ala-CN and Cys-Met-CN. The thiol function in a molecule adds onto the nitrile group of another one, allowing efficient condensation reactions and making available an extensive range of polymers containing amide bonds and/or five-membered heterocycles, namely thiazolines. Macrocycles were also identified, the biggest one containing sixteen residues (cyclo(Cys-Met)8). MALDI-TOF mass spectrometry was used to identify all the present species. What these examples show is that complex mixtures are likely to have formed on the primitive Earth and that, ultimately, the selection that must have followed may have been an even more crucial step towards life than the synthesis of the pre-biological species themselves.